Chemical investigation of ceylonese plants. Part XII. (+)-3,4prime;,5,7-Tetrahydroxy-3prime;-methoxyflavanone (+)-dihydroisorhamnetin and 3,5,7-trihydroxy-3prime;,4prime;-dimethoxyflavone (dillenetin): two new natural products fromDillenia indicaL.

摘要

612 J.C.S. Perkin IChemical Investigation of Ceylonese Plants. Part XII. (+)-3,4',5,7-Tetra hyd roxy-3'-met hoxyf lavanone and3,5,7-Trihydroxy-3',4'-dimethoxyflavone (Dillenetin) : Two New NaturalProducts from Dillenia indica L.[ ( + )-Oi hyd roisor hamnet in]By Gowsala Pavanasasivam and M. Uvais S. Sultanbawa,' Department of Chemistry, University of SriLanka, Peradeniya Campus, Peradeniya, Sri LankaThe title compounds [(I) and ( I I I ) ] have been obtained from the bark and pericarp of Dillenia indica L., respect-ively.As part of a programme of chemical studies on Ceyloneseplants, extractives of the bark and pericarp of Dilleniaindica L. (Dilleniaceae 2, have been studied, and two newnatural products have been isolated. The product fromthe bark was a pale yellow solid, C,,H,,O,, giving thecolour reactions of a flavanone and showing vmx 1640(CO) and 3340 and 3420 cm-l (OH).In the n.m.r.spectrum, two doublets at T 4.96 and 5.37 (each J 12 Hz)revealed that the compound was a 3-hydroxyflavanone.Signals at 7 2.90 (2'-H), 3.08 (6'-H), 3.22 (5'-H), 4.08(6-H), and 4-12 (8-H) suggested a 3',4',5,7-oxygenationpattern3 and the signal at T 6.22 showed that one ofthe oxygen functions was present as a methoxy-group.Positions 5 and 7 were ruled out for the methoxy-groupon the basis of U.V. spectral data: addition of aluminiumchloride caused a bathochromic shift in band I of 50 nm(5-OH) and NaOAc effected a bathochromic shift inband I1 of 38 nm (7-OH).4 Thus the methoxy-groupl Part XI, W.M. Bandaranayake, S. Selliah, M. U. S. Sultan-bawa, and D. E. Games, Phytochemistry, in .the press.a Cf. K. Kubitzki, Ber. Deut. Bot. Ges., 1968, 81, 238.T. J. Batterham and R. J. Highet, Azutmt. J . Chem., 1964,17, 428.was either at C-3' or -4'. This fact was confirmed bydiagnostically important mass spectral peaks at m/e(1){It) R-H{IIII R-Me318, 300, 166, 153, and 137.5 The position of themethoxy-group was established by oxidation of the4 T. J. Mabry in ' Perspectives in Phytochemistry.' eds. J . B.Harborne and T. Swain, Academic Press, London, 1969, p. 43.6 H. Audier, Bull. Soc. chim. France, 1966, 28921975 613compound with air in acidic medium to the correspond-ing flavonol methyl ether,6 which was identified as iso-rhamnetin (11) by comparison with an authentic sample.Hence the original compound was probably (+)-(2R,3R)-(2R,3R)-dihydroisorhamnetin] (I), in keeping with theabsolute configuration of other naturally occurring3-hydroxyflavanones .7The product isolated from the ethyl acetate extractof the pericarp was a flavone, C17H1407, vmX.1650 (CO)and 3290 and 3430 cm-l (OH). The n.m.r. spectrumindicated that it was a flavonol with two methoxy-groups and a 3,3’,4’,5,7-oxygenation at tern.^ Massspectral peaks at m/e 330, 315, 300, 165, 153, and 137showed that both methoxy-groups were in ring B.5From the above evidence, U.V. data, and its m . ~ . ~ , ~(290-292”), the compound was identified as the known3,5,7-trihydroxy-3’,4‘-dimethoxyflavone (3’,4’-di-O-methylquercetin) (111). The structure was confirmedby conversion into the pentamethyl ether, which wasidentical with an authentic sample of quercetin penta-methyl ether. This new natural product has beennamed dillenetin.Although the isolation of isorhamnetin (3’-0-methyl-quercetin) (11) from a large number of plants has beenreported, this is the first report of the isolation of(+)-dihydroisorhamnetin (I) lo and dillenetin (4’-0-methylisorhamnetin) (111) from natural sources.3,4’,5,7-tetrahydroxy-3’-methoxyi3avanone [(+)-EXPERIMENTALM.p.s were determined on a Kofler hot-stage apparatus.Microanalyses were carried out by the CSIRO Micro-analytical Service, Melbourne.Bark, timber, and fruits of D.indica L. were collectedfrom Hanguranketha, Kandy.Bark was separated fromthe timber, dried, chipped, and powdered in a mill. Thepencarp was separated from the fruit centre, chipped, anddried. The bark and pericarp were separately andsuccessively extracted with hot light petroleum, benzene,and methanol.Isolation of (+)-3,4‘,5,7-Tetrahydroxy-3‘-methoxyfl~vanone[( +)-Dihydroisovhamnelin] (I) .-An ethyl acetate extract ofthe methanolic extract of the bark was separated on asilica gel column with diethyl ether-light petroleum(35 : 65) and furnished a solid (0.002%). It was re-crystallised from aqueous ethanol to yield the fluvanone (I)as pale yellow crystals, m.p. 230°, [oiIDz7 $25” (in ethanol)(Found: C, 60.05; H, 4.4%; M+, 318-0745. Cl6HI40,requires C, 60.4; H, 4.4%; M , 318-0739); Amax.(MeOH)287 (log E 4.23) and 320 (3.89); A,, (MeOH-AlCl,) 311(4.34) and 370 (3.71) ; A,, (MeOH-AlC1,HCl) 311 (4.28)and 370 (3.69); A,,, (MeOH-NaOMe) 250 (4-23) and326 (3.80) ; A,, (MeOH-NaOAc) 290 (3.87) and 325 (4.01) ;Amax (MeOH-NaOAc-H,BO,) 290 (4.24) and 318 nm (3.95) ;T [(CD,),SO;2’-H);100 MHz] -2.87 (lH, S, &OH), 2.90 (lH, S,3.08 (lH, d, J 8 Hz, 6’-H), 3.22 (lH, d, J 8 Hz,J. C. Pew, J . Amer. Chem. Soc., 1948,70, 3031.J. W. Clark-Lewis and W. Korytnyk, J . Chem. SOC., 1958,2367.M. Krishnamoorthy, J. D. Ramanathan, T. R. Seshadri, andP. R. Shankaran, Indian J . Chem., 1965, 8, 270.L. Jurd, J . Org. Chem., 1962,27, 1294.5’-H), 4-08 (lH, d, meta-coupled, 6-H), 4.12 (lH, d, meta-coupled, 8-H), 4.96 (lH, d, J 12 Hz, 2-H), 6.37 (lH, d,J 12 €32, 3-H), and 6-22 (3H, s, OMe); m/e 318 (60%),300 (14), 289 (60), 166 (60), 153 (loo), and 137 (50).Treat-ment with iron(1zr) chloride gave a brown colour and withmagnesium-concentrated hydrochloric acid an orange-redcolour .Oxidation of ( + )-Dihydroisorhamnetin (I) .-( + )-Dihydro-isorhamnetin (0.015 g) in aqueous 2~-sulphuric acid (3 ml)was refluxed on a steam-bath, while a gentle stream of airwas passed over the liquid, for 24 h. After dilution withwater, the mixture was extracted with ethyl acetate andworked up. Recrystallisation from aqueous ethanol fur-nished isorhamnetin as a bright yellow solid (0.010 g),m.p. 298” (1it.,l1 305-307”), identical (mixed m.p., co-t.l.c.,and i.r. and U.V. spectra) with an authentic sample.Isolation of 3,5,7-Trihydroxy-3’, 4’-dimefhoxy$avone (Dil-lenetin) (111) .-An ethyl acetate extract of the methanolicextract of the pericarp was triturated with cold methanolt o remove betulinic acid.The filtrate was evaporatedand the residue refluxed with ethyl acetate and cooled.The deposited solid (0.007%) was recrystallised fromaqueous ethanol to give the flavone (111) as a bright yellowsolid, m.p. 290-292” (lit.,*p9 291-292”) (Found: C,61.6; H, 4.15%; M+, 330. Calc. for C1&&: C, 61.8;H, 4.25%; M , 330); Amx. (MeOH) 253 (log E 4-11), 267(4.01), and 365 (4.09); A,, (MeOH-AlCl,) 263 (4.20),360 (3-87), and 420 (4.13); A,, (MeOH-AlC1,-HCl) 260(4.15), 267 (4-14), 356 (3.87), and 420 (4.07); A,, (MeOH-NaOMe) 280 (4-09), 325 (3.85), and 414 (4.04);(MeOH-NaOAc-H,BO,) 255 (4.09), 266 (3.99), and 366 nm(4.05); T [(CD,),SO; 100 MHz] 2.20 (lH, d, J 9 Hz, 6’-H),2.26 (lH, S , 2’-H), 2-88 (lH, d, J 9 Hz, 5’-H), 3.52 (lH, d,meta-coupled, 6-H), 3.81 (lH, d, uneta-coupled, 8-H), and6.18 (2 x 3H, s, 2 x OMe); m/e 330 (loo%), 315 (25),300 (25), 287 (25), 259 (lo), 244 (lo), 165 (lo), 153 (8), and137 (5).Treatment with iron(II1) chloride gave an olive-green colour and with magnesium-concentrated hydro-chloric acid an orange colour.Methylation of 3,5,7- Trihydroxy-3’,4‘-dimethoxyfavone(III).-Compound (111) (0.05 g) in methanol (5 ml) wastreated with an excess of ethereal diazomethane and leftovernight. The residue obtained on evaporation wasseparated on a silica gel column with chlorof orm-benzene(1 : 1) and gave quercetin pentamethyl ether (0.025 g) aspale yellow needles (from methanol), m.p. 151-162”(1it.,l2 150-151”), identical (mixed m.p., i.r., and n.m.r.spectra, and t.1.c.) with an authentic sample.We thank Professor W. D. Ollis, F.R.S. (University ofSheffield), Professor R. H. Thomson (University of Aber-deen), and Dr. P. Bladon (University of Strathclyde) forspectroscopic data; and Dr. L. Horhammer (University ofMunchen) for an authentic sample of isorhamnetin. Thiswork has been supported by a grant from the NationalScience Council of Sri Lanka.[4/1697 Received, 13th August, 19743Cf. J. Chopin and G. Dellamonica, Compt. reled., 1970, 27M,11 H. Tatsuta and S. Fujise, Sci. Reports Tohoku Univ., 1966,l2 P. Suryaprakasa Rao, 0. B. Reddy, and T. R. Seshadri,631.(1) 39, 236.Proc. Indian Acad. Sci., 1940, 12A, 495